pusher listening for public channel

[AbdullahGhanem]

I get this error when listening for public channel

The following NoSuchMethodError was thrown while handling a gesture:
The method 'substring' was called on null.
Receiver: null
Tried calling: substring(0, 1)

When the exception was thrown, this was the stack:
#0 Object.noSuchMethod (dart:core-patch/object_patch.dart:51:5)
#1 EventFormatter.format (package:laravel_echo/src/util/event-formatter.dart:15:15)
#2 PusherChannel.listen (package:laravel_echo/src/channel/pusher-channel.dart:47:33)
#3 _PusherPage._listenToChannel (package:echo/pusher.dart:95:13)
#4 _PusherPage.build... (package:echo/pusher.dart:158:31)
...
Handler: "onTap"
Recognizer: TapGestureRecognizer#6a342
debugOwner: GestureDetector
state: possible
won arena
finalPosition: Offset(195.0, 793.3)
finalLocalPosition: Offset(175.0, 23.3)
button: 1
sent tap down